This thesis explores the use of familiar pre-composed music and unfamiliar improvised music in clinical music therapy with adults with acquired non- traumatic neurological illness. A detailed examination was made of six participants whose individual music therapy sessions spanned approximately six months. Clinical techniques used both songs and improvisation to explore issues pertinent to their lives. Primary data was collected in the form of focused interviews during and after music therapy sessions. Secondary sources of data included musical, behavioural and verbal material from the clinical sessions. Interview data was analysed using a modified form of Grounded Theory (Strauss and Corbin, 1990) to reveal emergent themes central to the participants' experiences of music therapy. Drawing from a neurobehavioural framework, analyses of the clinical material were made incorporating psychodynamic reflection through clinical supervision. This offered an alternative viewpoint and served as triangulation, in addition to checks with the multidisciplinary team. Open coding of the data established three major categories pertaining to the experience of the music, the experience of illness, and the emotional strategies to cope with illness. Three detailed case studies explored the relationships between these major categories using axial coding. The findings demonstrate that individuals living with chronic degenerative neurological illness find emotional meaning through the temporal relationship held with songs throughout their lives. Through songs which hold personal meaning, individuals are able to explore and express a wider range of emotional states than through words. Improvisation, on the other hand, possesses enhanced interactive properties pertaining specifically to the therapeutic relationship. Through playing and singing, individuals may monitor their physical selves. In this way, the therapist validates the individual's developing sense of 'self' through mutual music making, thereby shifting concepts of `self' from less able and damaged identities to identities which involved feelings of greater independence and ability.